Electric switches are known which comprise movable contacts consisting of two parallel contact arms which, in the closed position of the switch, are pressed by means of springs each against one side of two fixed knife-shaped contact bars arranged in spaced relationship to each other (see German Patent Specification No. 1,197,160). Since the two contact arms are traversed by current in the same direction, an electrodynamic contact pressure amplification is obtained, which eliminates the risk of contact lifting when the contacts are traversed by a short-circuit current. Such a switch having two parallel, movable contact arms gives a relatively cheap, simple and space-saving construction. However, it displays certain drawbacks, in particular upon making a short-circuit current. For such an operation, the known switch design is heavy to operate because of the electrodynamic attractive forces between the parallel current-traversed contact arms, which results in high friction between the contact surfaces.
In German Offenlegungsschrift No. 1,951,330 there is disclosed an auxiliary contact device with two parallel contact members, movable in opposite directions, which, in the closed position of the device, are pressed by means of springs each against one side of two fixed contact members arranged in spaced relationship to each other. Opening is effected by means of a wedge-shaped element, displaceable between the movable contact members, the contact members then moving perpendicular to the direction of displacement of the wedge-shaped element. This device employs movable contact members of circular cross-section which results, among other things, in the drawback that no defined closing and opening points are obtained, so that welding and burn damage may arise at any point on the contact surfaces.
The present invention aims to provide an improved electric switch of the kind referred to, in which the abovementioned drawbacks are avoided.